KABUL (Reuters) - A suicide bomber on a motorbike on Wednesday killed four people and wounded 10 in an attack on a vehicle carrying national security officials in the Afghan capital, police said.

Militant group Islamic State claimed responsibility for the attack, which occurred during morning rush hour in Kabul.

"The martyred brother Talha al-Khorsani was able to infiltrate a bus transporting elements from the apostate Afghani intelligence and detonated his explosive vest," Islamic State said in a statement posted on social media.

The attack highlighted the precarious security climate in Kabul, involving not only Islamic State and a Taliban insurgency but also a wider breakdown in law and order as government control has weakened.

(Reporting by Mirwais Harooni in KABUL and Mostafa Hashem in CAIRO; Writing by Randy Fabi; Editing by Clarence Fernandez)